Electric Field Waves
This has the solution: Ey = Eo sin(kx ? wt + fo)
and the phase velocity of this wave depends on the parameters of the space that the wave is going through: v = ?[1/(em)] .
Recall that eo = 1/(4pk) where k = 9 x 109 Nt-m2/Coul2 , and mo = 4p x 10-7 T-m/A .
Thus electric waves should propagate through vacuum with a speed of (you do the calculation).